The invention relates generally to control systems for internal combustion engines, and more particularly, concerns a powertrain controller for drive by wire vehicles.
For xe2x80x9cdrive by wirexe2x80x9d-equipped vehicles such as an electronic throttle control-equipped vehicle or variable valve timing-equipped vehicle, it is necessary to interpret driver demand and convert it to an appropriate engine control command to deliver the desired engine/vehicle response. For example, in a torque-based scheme, driver demand, as determined by the accelerator pedal input, is typically converted to a desired torque at the drive wheels. The desired torque of the wheels is then translated back to a desired engine torque using the steady-state gear ratio. Using the steady-state driveline gear ratio, however, ignores acceleration and shift transients in the driveline. It also does not account for the torques applied by the various clutches and band friction elements in the transmission and driveline. As a result, drivability may be compromised. In addition, extensive calibrating or xe2x80x9ctuningxe2x80x9d of controller parameters is usually required to provide acceptable performance. Accordingly, there is a need for an improved powertrain output controller.
Accordingly, it is an object of the present invention to provide an improved powertrain output controller.
According to the present invention, the foregoing and other objects and advantages are attained by an engine output control method for a vehicle having a drive by wire engine system responsive to a desired engine torque signal. The method comprises the steps of generating a driver demanded acceleration value corresponding to an operator input, and generating a gear value as a function of a vehicle speed value and the driver demanded acceleration value. The method also derives a driveline torque demand comprising an inertial model torque value of the vehicle driveline corresponding to the driver demanded acceleration and the gear value, and a dynamic transmission model torque value for the gear value. The resulting torque demand is then passed through an inverse torque converter model to generate a demanded engine torque. The resulting demanded engine torque value is then used to control the engine output. In this way, the present method accounts for the transmission and driveline dynamics in an acceleration-based engine control scheme.
An advantage of the present invention is that it provides an improved powertrain output controller which accounts for transmission and driveline dynamics. Another advantage of the present invention is that it reduces the calibration effort of the engine controller and improves performance.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims and upon reference to the accompanying drawings.